datasette/tests/conftest.py
Alex Garcia 8b35d4a80d Add OpenTelemetry metrics for SQL thread pool saturation and query latency
Spans describe requests that have finished. They structurally cannot answer
"am I saturating my 3 SQL threads right now", because that is a level rather
than an event - and with num_sql_threads defaulting to 3, it is usually the
first thing worth knowing about a busy Datasette. This adds the metrics that
answer it.

Five observable gauges, computed only when something is collecting, so an
instance with no MeterProvider installed does no work for them at all:

  datasette.sql.threads.limit         num_sql_threads
  datasette.sql.threads.queue_depth   queries waiting for a free thread
  datasette.sql.queries.pending       in-flight reads, by db.namespace
  datasette.write.queue_depth         writes behind the single write thread
  datasette.connections.open          tracked file connections

Three instruments recorded inline, which matters because metrics survive
trace sampling and spans do not - an operator sampling 1% of traces still
gets 100% of the latency distribution:

  db.client.operation.duration        semconv histogram, with error.type
  datasette.write.queue_wait          the metric twin of the existing span
  datasette.sql.queries.interrupted   sql_time_limit_ms kills

The interrupted counter closes a gap the plan called out as unanswerable:
"how often are we killing queries at the limit" is a rate, and a rate cannot
be recovered from sampled spans.

Core still creates no provider of any kind, so the architecture is unchanged;
`grep -rn 'opentelemetry.sdk' datasette/` stays empty. One real difference
from tracing is worth recording: _ProxyMeter and its instruments forward to a
provider installed after they were created, whereas ProxyTracer permanently
caches the first concrete tracer it resolves. Module-level instruments are
therefore safe and the test fixture has no ordering constraint.

Live instances are tracked in a lock-guarded WeakSet so instrumenting an
instance never keeps it alive. The pool gauges carry no attribute saying
which Datasette produced them: production runs one instance per process, and
adding an id to disambiguate the test suite's hundreds of instances would buy
unbounded attribute cardinality to fix a case that does not occur. The
collision is documented instead, and the gauge callbacks are plain generator
functions so tests can assert exact values by calling them directly rather
than through the SDK's last-value aggregation.

demos/otel/metrics_demo.py fires 12 concurrent 40ms queries at a 3-thread
pool and samples the gauges mid-flight: queue_depth peaks at exactly 9, and
the duration histogram reads max=0.1695s for a query whose work is 40ms. That
gap is the queue, and it is the thing traces alone will not show you.

Also corrects the demo README's privacy section, which still claimed
parameter values are never recorded - that stopped being unconditionally true
when trace_sql_parameters landed.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

(cherry picked from 6ef0dd8c and adapted to the rebuilt phase-1 stack:
attribute names now come from telemetry_registry where entries exist, the
meter carries the instrumentation-scope version and schema URL, and the
interrupted-queries counter skips expected timeouts - callers that opted
into a deliberately short budget, like facet suggestion - matching how
those are excluded from span error status. The internals.rst reference
lands with the registry commit that follows.)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01F2h9ANGZ7paWSpqs5DUAcG
2026-09-01 17:09:35 -07:00

565 lines
19 KiB
Python

import importlib.metadata
import os
import pathlib
import re
import socket
import subprocess
import sys
import tempfile
import time
from dataclasses import dataclass
import httpx
import pytest
import pytest_asyncio
from datasette import Event, hookimpl
try:
import pysqlite3 as sqlite3
except ImportError:
import sqlite3
UNDOCUMENTED_PERMISSIONS = {
"this_is_allowed",
"this_is_denied",
"this_is_allowed_async",
"this_is_denied_async",
"no_match",
# Test actions from test_hook_register_actions_with_custom_resources
"manage_documents",
"view_document_collection",
"view_document",
}
def wait_until_responds(url, timeout=5.0, client=httpx, process=None, **kwargs):
start = time.time()
while time.time() - start < timeout:
# If the server died there is no point waiting out the timeout - fail
# now, with its output, instead of after `timeout` seconds of silence
if process is not None and process.poll() is not None:
raise AssertionError(
"Server exited early with returncode {}\n{}".format(
process.returncode, process.stdout.read().decode("utf-8")
)
)
try:
client.get(url, **kwargs)
return
except httpx.TransportError:
time.sleep(0.1)
raise AssertionError(f"Timed out waiting for {url} to respond")
def find_free_port():
with socket.socket() as sock:
sock.bind(("127.0.0.1", 0))
return sock.getsockname()[1]
_otel_span_exporter = None
@pytest.fixture(scope="session", autouse=True)
def _otel_provider():
"""
Install a real OTel SDK TracerProvider + InMemorySpanExporter exactly
once, before any span is ever created in this process.
This has to be session-scoped and autouse because
`opentelemetry.trace.set_tracer_provider()` is effectively
once-per-process: a second call logs a warning and is ignored. So the
install must happen exactly once, before anything asserts on spans.
`datasette.telemetry.tracer` is a module-level `ProxyTracer`. Once a
provider exists, the first span it starts resolves a concrete tracer
and caches it permanently. It does *not* cache the no-op tracer, so
any span started before this fixture runs is merely lost rather than
poisoning the tracer for the rest of the process. If the SDK isn't
installed, do nothing: core spans stay no-op `NonRecordingSpan`s and
the rest of the suite is unaffected.
"""
global _otel_span_exporter
try:
from opentelemetry import trace as otel_trace
from opentelemetry.sdk.trace import TracerProvider
from opentelemetry.sdk.trace.export import SimpleSpanProcessor
from opentelemetry.sdk.trace.export.in_memory_span_exporter import (
InMemorySpanExporter,
)
except ImportError:
return
exporter = InMemorySpanExporter()
provider = TracerProvider()
# SimpleSpanProcessor exports synchronously on span end - no background
# batching thread, so assertions immediately after a request never race.
provider.add_span_processor(SimpleSpanProcessor(exporter))
otel_trace.set_tracer_provider(provider)
_otel_span_exporter = exporter
@pytest.fixture
def otel_spans():
"""
Function-scoped access to the finished-spans exporter: clears any spans
left over from previous tests, then yields the exporter so a test can
call `.get_finished_spans()` after making requests. Skips (rather than
fails) if the OTel SDK is not installed.
"""
pytest.importorskip("opentelemetry.sdk")
if _otel_span_exporter is None:
pytest.skip("OpenTelemetry SDK provider was not installed")
_otel_span_exporter.clear()
yield _otel_span_exporter
_otel_metric_reader = None
@pytest.fixture(scope="session", autouse=True)
def _otel_meter_provider():
"""
Install a real OTel SDK MeterProvider + InMemoryMetricReader once per
process.
Unlike the tracer, ordering is not load-bearing here: `_ProxyMeter` and
the `_ProxyInstrument`s it hands out forward to a provider installed
*after* they were created, whereas `ProxyTracer` permanently caches the
first concrete tracer it resolves. This fixture is still session-scoped
and autouse for symmetry, and so that a single reader collects for the
whole run.
DELTA temporality is chosen for counters and histograms so that each
collection reports only what happened since the previous one. With the
SDK default of CUMULATIVE, every metrics test would see every query run
by every earlier test in the session.
"""
global _otel_metric_reader
try:
from opentelemetry import metrics as otel_metrics
from opentelemetry.sdk.metrics import Counter, Histogram, MeterProvider
from opentelemetry.sdk.metrics.export import (
AggregationTemporality,
InMemoryMetricReader,
)
except ImportError:
return
reader = InMemoryMetricReader(
preferred_temporality={
Counter: AggregationTemporality.DELTA,
Histogram: AggregationTemporality.DELTA,
}
)
otel_metrics.set_meter_provider(MeterProvider(metric_readers=[reader]))
_otel_metric_reader = reader
class MetricsCollector:
"""
Thin reader over an `InMemoryMetricReader`.
`collect()` runs a collection cycle - which is what invokes the observable
gauge callbacks - and snapshots the result. Queries then run against that
snapshot rather than re-collecting, so a test that inspects several
metrics sees one consistent moment and does not drain delta state twice.
"""
def __init__(self, reader):
self.reader = reader
self.snapshot = {}
def collect(self):
self.snapshot = {}
data = self.reader.get_metrics_data()
if data is None:
return self.snapshot
for resource_metrics in data.resource_metrics:
for scope_metrics in resource_metrics.scope_metrics:
for metric in scope_metrics.metrics:
self.snapshot.setdefault(metric.name, []).extend(
metric.data.data_points
)
return self.snapshot
def points(self, name, attributes=None):
"Data points for `name` whose attributes are a superset of `attributes`."
found = []
for point in self.snapshot.get(name, []):
point_attributes = dict(point.attributes or {})
if all(point_attributes.get(k) == v for k, v in (attributes or {}).items()):
found.append(point)
return found
def point(self, name, attributes=None):
"The single matching data point, asserting there is exactly one."
found = self.points(name, attributes)
assert len(found) == 1, (
f"expected exactly one {name} point matching {attributes}, "
f"got {len(found)}: {found}"
)
return found[0]
@pytest.fixture
def otel_metrics():
"""
Function-scoped metrics collector. Drains any delta state accumulated by
earlier tests before yielding, so counts start from zero.
"""
pytest.importorskip("opentelemetry.sdk")
if _otel_metric_reader is None:
pytest.skip("OpenTelemetry SDK meter provider was not installed")
_otel_metric_reader.get_metrics_data()
yield MetricsCollector(_otel_metric_reader)
@pytest.fixture
def bare_ds():
"""
Minimal Datasette with no plugins, data, metadata, or config - for tests
that want to exercise core behavior (e.g. middleware) in isolation.
"""
from datasette.app import Datasette
return Datasette(memory=True)
@pytest_asyncio.fixture(scope="session")
async def ds_client():
import secrets
from datasette.app import Datasette
from datasette.database import Database
from .fixtures import CONFIG, METADATA, PLUGINS_DIR
ds = Datasette(
metadata=METADATA,
config=CONFIG,
plugins_dir=PLUGINS_DIR,
settings={
"default_page_size": 50,
"max_returned_rows": 100,
"sql_time_limit_ms": 200,
"facet_suggest_time_limit_ms": 200, # Up from 50 default
# Default is 3 but this results in "too many open files"
# errors when running the full test suite:
"num_sql_threads": 1,
},
)
from datasette.fixtures import populate_fixture_database
# Use a unique memory_name to avoid collisions between different
# Datasette instances in the same process, but use "fixtures" for routing
unique_memory_name = f"fixtures_{secrets.token_hex(8)}"
db = ds.add_database(Database(ds, memory_name=unique_memory_name), name="fixtures")
ds.remove_database("_memory")
def prepare(conn):
if not conn.execute("select count(*) from sqlite_master").fetchone()[0]:
populate_fixture_database(conn)
await db.execute_write_fn(prepare)
await ds.invoke_startup()
return ds.client
def pytest_report_header(config):
conn = sqlite3.connect(":memory:")
version = conn.execute("select sqlite_version()").fetchone()[0]
conn.close()
sqlite_utils_version = importlib.metadata.version("sqlite-utils")
headers = [
f"SQLite: {version}",
f"sqlite-utils: {sqlite_utils_version}",
]
if config.getoption("--playwright"):
try:
browsers = config.getoption("--browser")
except ValueError:
browsers = None
if isinstance(browsers, str):
browsers = [browsers]
if browsers:
headers.append("Playwright browsers: {}".format(", ".join(browsers)))
return headers
def pytest_addoption(parser):
parser.addoption(
"--playwright",
action="store_true",
default=False,
help="run Playwright browser automation tests",
)
def pytest_configure(config):
import sys
sys._called_from_test = True
def pytest_unconfigure(config):
import sys
del sys._called_from_test
def pytest_collection_modifyitems(config, items):
if not config.getoption("--playwright"):
skip_playwright = pytest.mark.skip(reason="need --playwright option to run")
for item in items:
if "playwright" in item.keywords:
item.add_marker(skip_playwright)
# Ensure test_cli.py and test_black.py and test_inspect.py run first before any asyncio code kicks in
move_to_front(items, "test_cli")
move_to_front(items, "test_black")
move_to_front(items, "test_inspect_cli")
move_to_front(items, "test_serve_with_get")
move_to_front(items, "test_serve_with_get_exit_code_for_error")
move_to_front(items, "test_inspect_cli_writes_to_file")
move_to_front(items, "test_spatialite_error_if_attempt_to_open_spatialite")
move_to_front(items, "test_package")
move_to_front(items, "test_package_with_port")
# Same reason: this one shells out to a fresh interpreter. Late in a serial
# run the pytest process holds enough threads that the fork half of
# subprocess' fork+exec crashes the interpreter on macOS/CPython 3.13
# (SIGSEGV/SIGBUS inside _execute_child). Reproduces with any subprocess
# call placed there, on an unmodified tree - running it first avoids it.
move_to_front(items, "test_datasette_package_never_imports_the_sdk")
move_to_front(items, "test_no_provider_takes_the_fast_path")
def move_to_front(items, test_name):
test = [fn for fn in items if fn.name == test_name]
if test:
items.insert(0, items.pop(items.index(test[0])))
@pytest.fixture
def restore_working_directory(tmpdir, request):
try:
previous_cwd = os.getcwd()
except OSError:
# https://github.com/simonw/datasette/issues/1361
previous_cwd = None
tmpdir.chdir()
def return_to_previous():
os.chdir(previous_cwd)
if previous_cwd is not None:
request.addfinalizer(return_to_previous)
@pytest.fixture(scope="session", autouse=True)
def check_actions_are_documented():
from datasette.default_actions import register_actions as default_register_actions
from datasette.plugins import pm
content = (
pathlib.Path(__file__).parent.parent / "docs" / "authentication.rst"
).read_text()
permissions_re = re.compile(r"\.\. _actions_([^\s:]+):")
documented_actions = set(permissions_re.findall(content)).union(
UNDOCUMENTED_PERMISSIONS
)
# Only Datasette core actions need to be documented - actions registered
# by (test) plugins are checked for registration but not documentation
core_actions = {action.name for action in default_register_actions()}
def before(hook_name, hook_impls, kwargs):
if hook_name == "permission_resources_sql":
datasette = kwargs["datasette"]
assert kwargs["action"] in datasette.actions, (
"'{}' has not been registered with register_actions()".format(
kwargs["action"]
)
+ " (or maybe a test forgot to do await ds.invoke_startup())"
)
action = kwargs.get("action").replace("-", "_")
if kwargs["action"] in core_actions:
assert (
action in documented_actions
), f"Undocumented permission action: {action}"
pm.add_hookcall_monitoring(
before=before, after=lambda outcome, hook_name, hook_impls, kwargs: None
)
class TrackEventPlugin:
__name__ = "TrackEventPlugin"
@dataclass
class OneEvent(Event):
name = "one"
extra: str
@hookimpl
def register_events(self, datasette):
async def inner():
return [self.OneEvent]
return inner
@hookimpl
def track_event(self, datasette, event):
datasette._tracked_events = getattr(datasette, "_tracked_events", [])
datasette._tracked_events.append(event)
@pytest.fixture(scope="session", autouse=True)
def install_event_tracking_plugin():
from datasette.plugins import pm
pm.register(TrackEventPlugin(), name="TrackEventPlugin")
@pytest.fixture(scope="session")
def ds_localhost_http_server():
ds_proc = subprocess.Popen(
[sys.executable, "-m", "datasette", "--memory", "-p", "8041"],
stdout=subprocess.PIPE,
stderr=subprocess.STDOUT,
# Avoid FileNotFoundError: [Errno 2] No such file or directory:
cwd=tempfile.gettempdir(),
)
wait_until_responds("http://localhost:8041/")
# Check it started successfully
assert not ds_proc.poll(), ds_proc.stdout.read().decode("utf-8")
yield ds_proc
# Shut it down at the end of the pytest session
ds_proc.terminate()
@pytest.fixture(scope="session")
def ds_unix_domain_socket_server(tmp_path_factory):
# This used to use tmp_path_factory.mktemp("uds") but that turned out to
# produce paths that were too long to use as UDS on macOS, see
# https://github.com/simonw/datasette/issues/1407 - so I switched to
# using tempfile.gettempdir() with a per-process filename.
uds = str(pathlib.Path(tempfile.gettempdir()) / f"datasette-{os.getpid()}.sock")
try:
os.unlink(uds)
except FileNotFoundError:
pass
ds_proc = subprocess.Popen(
[sys.executable, "-m", "datasette", "--memory", "--uds", uds],
stdout=subprocess.PIPE,
stderr=subprocess.STDOUT,
cwd=tempfile.gettempdir(),
)
# Poll until available
transport = httpx.HTTPTransport(uds=uds)
client = httpx.Client(transport=transport)
try:
wait_until_responds(
"http://localhost/_memory.json", timeout=30.0, client=client
)
# Check it started successfully
assert not ds_proc.poll(), ds_proc.stdout.read().decode("utf-8")
yield ds_proc, uds
finally:
client.close()
# Shut it down at the end of the pytest session
ds_proc.terminate()
try:
ds_proc.wait(timeout=5)
except subprocess.TimeoutExpired:
ds_proc.kill()
ds_proc.wait()
try:
os.unlink(uds)
except FileNotFoundError:
pass
@pytest.fixture
def serve_with_plugins(tmp_path):
"""Factory fixture for starting ``datasette serve`` in a subprocess with
plugins written to a temporary ``--plugins-dir``.
For tests that need the real serve path: event-loop wiring, exit codes,
signals. The usual in-process ``pm.register`` plugin pattern can't reach
a subprocess, so plugin source is written out as importable files instead.
Unlike ``ds_localhost_http_server`` this is function-scoped and takes a
fresh port each time, because each test needs its own plugins. Call it as::
proc, port = serve_with_plugins({"my_plugin": PLUGIN_SOURCE})
``plugins`` maps module name to Python source. Pass
``wait_for_startup=False`` when the server is expected to fail during
startup rather than begin serving. Extra CLI arguments are passed through.
Every process started is terminated when the test ends.
"""
processes = []
def start(plugins, *extra_args, wait_for_startup=True):
plugins_dir = tmp_path / "plugins"
plugins_dir.mkdir(exist_ok=True)
for module_name, source in plugins.items():
(plugins_dir / f"{module_name}.py").write_text(source, "utf-8")
port = find_free_port()
proc = subprocess.Popen(
[
sys.executable,
"-m",
"datasette",
"--memory",
"--plugins-dir",
str(plugins_dir),
"-h",
"127.0.0.1",
"-p",
str(port),
*extra_args,
],
stdout=subprocess.PIPE,
stderr=subprocess.STDOUT,
# Avoid FileNotFoundError: [Errno 2] No such file or directory:
cwd=tempfile.gettempdir(),
)
processes.append(proc)
if wait_for_startup:
wait_until_responds(
f"http://127.0.0.1:{port}/-/versions.json", process=proc
)
return proc, port
yield start
for proc in processes:
if proc.poll() is None:
proc.terminate()
try:
proc.wait(timeout=5)
except subprocess.TimeoutExpired:
proc.kill()
proc.wait()
# Import fixtures from fixtures.py to make them available
from .fixtures import ( # noqa: F401
TEMP_PLUGIN_SECRET_FILE,
app_client,
app_client_base_url_prefix,
app_client_conflicting_database_names,
app_client_csv_max_mb_one,
app_client_immutable_and_inspect_file,
app_client_larger_cache_size,
app_client_no_files,
app_client_returned_rows_matches_page_size,
app_client_shorter_time_limit,
app_client_two_attached_databases,
app_client_two_attached_databases_crossdb_enabled,
app_client_two_attached_databases_one_immutable,
app_client_with_cors,
app_client_with_dot,
make_app_client,
)